Engine control system



May 21, 1946.

E. c. WAHLBERG ENGINE CONTROL SYSTEM Filed 001:. 50, 1943 2 Sheets-Sheet l INVENTOR. WW

M ATTORNEY.

y21 1946. 4 EQ c. WAHLBERG 2,400,580

. ENGINE CONTROL SYSTEM wr omgx Patented May 21, 1946 UNITED STATES PATENT OFFICE ENGINE CONTROL SYSTEM Application October 30, 1943, Serial No. 508,425

17 Claims.

The present application is a continuation-inpart of my copending application, Serial No. 501,405 filed September 6, 1943, and relates back thereto for all common subject matter.

in my copending application there is disclosed a control system whereby the speeds of a plurality of prime movers, such as the internal combustion engines on a multi-engine aircraft, may be varied in substantial synchronism. As shown in said application, the speed of each engine is controlled by an individual governor, and the settings of all the governors may be varied in synchronism in order to accomplish substantially synchronous changes in speeds of the engines.

In a multiengine aircraft it is also desirable to have it possible to vary the speeds of the various engines independently, usually under the control of an oliicer other than the pilot, such as the flight engineer, for the purpose of testing the several engines. However, it is also desirable that the pilot be able to take the control away from the flight engineer instantaneously at any time and to re-synchronize the engines.

In accordance with the present invention, a separate switch is provided by means of which the settings of the several governors may be varied independently of each other to thereby individually adjust the speeds of the engines controlled by the respective governors. However, the pilot is always able to re-synchronize the engines by simply manipulating the same control member as is employed to change their synchronous speeds.

Further objects and advantages of my invention will be apparent from the following description considered in connection with the accompanying drawings, which form a part of this specification, and of which;

Fig. 1 is a straight-line style of wiring diagram illustrating a preferred embodiment of my invention;

Fig. la is an explanatory key for the relays embodied in Fig. 1. In the key the contacts of each relay are shown in vertical alignment with each other and with the solenoid or heating element which actuates them, contacts located above the broken line being those employed in the control circuits shown in the left portion of Fig. 1, while the contacts located below this line are those employed in the motor circuits shown in the right portion of Fig. 1; and

Fig. 2 is a schematic wiringdiagram of one of the motors shown in Fig. 1.

In Fig. l, numerous magnetic and thermorelays are schematically shown. The solenoids of the magnetic relays are shown as coils, while heating elements of the thermorelays are shown as a series of straight lines joined at angles of The solenoids and heating elements are designated by capital lettersand the various contacts forming parts of the different relays are designated by the same capital letter which designates the solenoid or heating coil of that relay with a number added thereto. Thus, the contacts actuated by the solenoid A are designated A1 and A2. (Iontacts which are normally open, that is when the coil of the relay is not energized, are shown as two spaced rectangles, such as contact A2, while contacts which are normally closed are shown by two contiguous rectangles, such as contact A1.

Reference character Ill designates a conductor for supplying suitable current for energizin the various relay coils. The heating coil B of a thermorelay is connected in series with the normally closed contact A1 and the normally open contact C2 between the conductor l0 and ground. The solenoid C of a magnetic relay is connected to the conductor l0 through the normally closed contact B1 and to ground through the normally open contacts A2 and 01 connected in parallel.

The solenoid D is connected to the conductor I0 through a limit switch I2, the function and operation of which will be explained hereinafter. The other side of the solenoid D is connected to the pole I4 of a double throw switch I6, and through a normally open contact P1 to ground.

The solenoid E is connected through a limit switch I8 to the conductor It and the other side of the solenoid is connected to the pole 20 of the switch I6, and through the normally open contact Q1 to ground. The solenoid F is connected to the conductor I 0 through a limit switch 22 and the other side is connected to the pole 24 of a double throw switch 26, and through the normally open contact P2 to ground. The solenoid G is connected through a limit switch 28 to conductor It and the other side is connected to the pole 30 of switch 26, and through the normally open contact Q2 to ground.

The blades of switches I6 and 26 are connected together by means of a conductor 32, which is connected through normally closed contact Y1 and the solenoid A to ground. The solenoid A may be connected to the line I0 through the normally open contact Y2 connected in series with a resistor II having the same resistance as the solenoids D, E, F or G.

The solenoid K is connected directly to the line and to ground through a normally open limit switch [2 and a pair of parallel connected, signal bulbs 46 and 4B, and through a normally open limit switch 22 and a pair of signal lamps 50 and 52. Solenoid L is connected directly to conductor l and through normally open limit switches l8 and 28' and signal lamps 4t and 48, and E8 and 52', respectively, to ground.

Reference character 54 designates a switch which is generally similar to the switch disclosed in my aforesaid copending application. This switch includes a rotatabl mounted disc 56 on which is mounted contact segments 58 and 60. This disc may be rotated by means of a pinion G2 driven by an electric motor to be subsequently described. A manually turnable contact arm 64. is mounted concentrically with respect to disc 56, but independently thereof so that turning of the arm does not rotate the disc and rotation of the disc does not turn the arm. Switch 54 also includes normally open limit switches 66 and 58 which are so arranged as to be closed when the arm 64 is turned to its extreme right or left positions, respectively.

The solenoid M is connected to the conductor is through the normally closed contact L1 and to the contact segment 58 of switch 54 through the normally closed contact Y3. The solenoid N is connected to the conductor is through the normally closed contact K1, and to the segment 68 through the normally closed contact Y5. lhe solenoids P and Q are connected to the conductor Ill through the normally closed contacts M1 and N1 in series. The solenoid P is connected to the Contact seg ment 60 through the normally opencontactYn, and to ground through the normally open contact P and resistor 69, while the solenoid Q is connected to the contact segment 58 through the normally open contact Y4, and to ground through the nor mall open contact Q5 and the resistor iii,

A conductor is connected to conductor if through the normally open contacts R1 and T1 in parallel, While the solenoid R is connected to the conductor I0 through the normall open contacts M2 and N2 in parallel.

A conductor I2 is connected t the conductor l0 through the normally open contacts M3, N3 and U1 in parallel. The heating element T of a thermo relay is connected through the normally closed contact R2 to the conductor 12, the other side of the coil being grounded. The solenoid U is connected to the conductor 12 through the normally closed contacts W1 and Y7. the other side of the solenoid being grounded.

The heating coil W of a thermo relay is connected between the conductor is and ground and in series with the normally closed contact Mr and N4 and the normally open contact Us.

The solenoid Z is connected in serie with the normally closed contacts P4 and Q4 between the arm 64 and ground. A signal lamp M is shunted around solenoid Z and the contacts P4 and Q4. Shunted in a similar manner are the solenoids H and J connected in series with normally open contacts P3 and Q3, respectively. The resistance of resistor 89 is equal to the resistance offered by the parallel circuit comprising the signal lamp "M and the solenoids Z, H r J. One of the contacts of each of the limit switches 55 and 63 are connected directly to the line It). The other contacts of these limit switches are connected together and through the solenoid Y to ground. In other words, the switches 68 and 63 are connected in parallel between the line l6 and the solenoid Y.

Reference character 83 designates a conductor for supplying suitable current for operating the electric motors. A conductor 3?: is connected to conductor 36 through normally open contacts and Us in paralle. As shown, there are t e motors having commutators =94 ard 85, p irs of slip rings 9d and ii respectively, and field windings M, and respectively.

The field windings are connected in parallel, one side bein grounded while the other side is connected to the conductor The slip rings 58 are connected between conductor 19:] and I62 through normally open contacts Us and U4. rings 557 are connected between the conductors throu d1 normally open contacts U5 and Us, while slip ring are connected between conductors B and 32 through normall open contacts U7 and Us. Conductor Hill is connec ,ed to ground through normall closed contact and normally open contact U10 in series. Conductor it?! is connected to the conductor 99 through the normally closed contacts B3.

A conductor lot is connected to the conductor 9:) through the normally open ontact M5 and Eli in series, and to ground through the normaliy open contacts N6, Re and U10 in series. A conductor is connected to conductor 9 through normally open contacts N5 and R5 in series, and to ground through normally open contacts Mt, Re and U10 in series.

Co-mmutator ill is connected between conductors Hi4 and H36 through normally open contacts Z1 and Z4. Commutator M is connected between these conductors through normally open contacts Z5 and Z8, whil commutator 36 is connected bctween conductors 1M and its through normally open contacts Z9 and Z12.

lA. conductor lid is connected directly to ground and a conductor 1 it! is connected directly to the line 211 The upper brush of armature 82 may be connected to the ground wire 583 through n0rmally closed contact Z2 an: normally open contact H3, or to conductor H3 through normally closed contact Z2 and normally open contact J2. The other brush of commutator 82 may be connected to the conductor Hal through normally closed contact Z3 and normall open contact L), or to the ground wire H33 through normall closed contact Z3 and normally open contact J3. The brushes of this commutator may be connected together to short circuit the armature of the motor through normally closed contacts Z2, H1, J1 and Z3. Similar connections are provided for commutators 8 and 86, whereby these commutators may be connected across conductor Hi8 and Hi] and the polarity of the armature-s with respect to these conductors may be reversed.

As shown, the motor having commutator 82 drives the pinion which as above described. is arranged to rotate the disc of switch The remaining motors may be connected, as is shown for one motor in Fig. 2, to drive a pinion H2 which engages a rack. M4 arranged to vary the tension on the speeder spring I15 of a governor. As is well known, the governor is driven by a prime mover, such an internal combustion cngine, and is arranged to maintain the speed of the engine constant in any preferred manner. is disclosed in my above mentioned copending application, the governor controls the pitch of a propeller driven by the internal combustion engine.

Also illustrated in Fig. 2 is the arrangement of the limit switches l2, I2, 3 and I8, which are associated with the motor there shown. Rack l I4 is provided with arms H3 and I20, arranged to actuate the limit switches when the rack is at the limits of its travel. Thus, when the rack is moved to the left as viewed in the figure, so as to increase to a maximum the tension of spring Hii the arm H8 will open limit switch l2, and close limit switch l2. On the other hand, when the rack has been moved to the right so as to decrease to a minimum the tension on the spring lit, the arm IE9 will open limit switch l8 and close limit switch it. Increasing the tension of the speeder spring increases the speed of the engine, and vice versa, as is well known.

Fig. 2 also shows the manner in which the slip rings are connected to fixed taps on the armature winding of the motor. As is fully explained in my copending applications, Serial No. 428,018 filed January 24, 1942, and Serial No. 472,46 filed January 15, 1943, when current is applied to the armature winding through the slip rings, the field being excited, the armature will line up in a predetermined position with respect to the field. Moreover, if a plurality of these motors have their respective slip rings connected in parallel, they run in synchronism with each other when current is applied to the armature through the brushes.

The above described device operates as follows:

It will first be assumed that the governor settings, as determined by the tension of the speeder springs, is the same and consequently the governors maintain the internal combustion engines in synchronism with each other at a speed determined by the governor settings. Should the pilot wish to change the speed of the several engines, he moves the contact arm 64 in one direction or the other, depending upon whether he wishes to increase or decrease the engine speed, and it is assumed that movement in a clockwise direction into contact with segment 66 results in an increase in speed. Contact between arm 64 and segment establishes a circuit from ground through normally closed contacts P4, Q4, solenoid Z, normally closed contact Y5, solenoid N and normally closed contact E1 to the line Ill, thus energizing solenoids N and Z and lighting the signal lamp M which is in parallel with solenoid Z. Consequently, contacts N1 and N4 are opened, while contacts N2, N3, N5 and N6 are closed, and. contacts Z2, Z3,

Z6, Z7, Z10 and Z11 are opened, while contacts Z1,

Z4, Z5, Z8, Z9 and Z12 are closed.

Closing of N2 does not immediately energize solenoid R because contacts R1 and T1 are both open. However, closing of contact N3 does immediately energize solenoid U through the normally closed contacts W1 and Y7 with the result that all of the U contacts are closed. Closing of U9 supplies current from the line 86 to the field windings 94, 9B and 98 and also to the conductor is: through the normally closed contact R3. Closing of U10 connects the conductor me to ground through the normally closed contact R4. Inasmuch as contacts Us to Us have been closed, the slip rings 88, 90 and 92 are connected across the conductors IM! and (02 and hence current is supplied through the slip rings to position the several armatures with respect to their fields, as explained above in connection with Fig. 2. During this positioning period current is not supplied to the armatures through their commutators, because contacts R5 and Rs are still open, although contacts N5 and Ne have been closed.

Closing of N3 also supplies current to the heating coil T. A certain length of time is required for the heating of this coil, which time is suiiicient for the above described positioning of the armatures to take place. Thereupon, contact T1 is closed, thus completing the circuit from the line through closed contact N2 to solenoid R. Energization of this solenoid closes contact R1 to provide a holding circuit for solenoid R, and opens contact R2 to drop out heating element T. Cooling of this element opens contact T1, but solenoid R remains energized because R1 has been closed. Contacts R2 and R4 are opened, thus disconnecting the slip rings from the line. However, the slip rings remain connected together in parallel due to the fact that contacts Us through Us are closed. Contacts R5 and Re are closed by the energization of solenoid R and consequently conductor Hi4 is connected to ground and conductor IE6 is connected to the line 89. The closing of contacts Z1, Z4, Z5, Z8, Z9 and Z12 connects the upper brush or each commutator to ground through the conductor I94, and connects the lower brush to the line 86 through conductor l as. The opening of contacts Z2, Z3, Z6, Z7, Z10 and Z11 removes a short circuit of each of the commutators, and the motors operate in the proper direction to increase the tension on the speeder springs of the governors, and to drive the disc 58 in a clockwise direction. Due to the fact that the slip rings are connected in parallel, all of the motors operate in synchronism and hence the settings of the governors are changed by equal amounts.

Disc 5% is rotated until the insulated space between the segments and E is turned into alignment with the arm (it, which was turned by the pilot a certain distance in a clockwise direction. The further the arm 64 was turned, the greater the angle through which the disc 55 must be rotated by the motor and consequently the greater the change in governor setting effected b the other motors. Therefore, the angle through which the arm is turned is a measure of the speed change and a suitably calibrated scale may be provided in order to show the position to which the arm 64 should be turned for any desired speed of the engines.

When contact between arm 64 and segment 60 is broken by the above described rotation of disc 55, solenoids Z and N are de-energized and hence contacts N5, N6, Z1, Z4, Z5, Z8, Z9 and Z12 are open d, thus interrupting the supply of current to the several commutators. At the same time, contacts Z2, Z3, Z6, Z7, Z10 and Z11 are closed and consequently the several armatures are short circuited through these contacts and, normally closed contacts H1, J1, F1, G1, D1 and E1. This provides dynamic braking circuits which very rapidly decelerate the motors so as to prevent any tendency to coast.

De-energization of solenoid N also opens contact N2, thus de-energizing solenoid R, which closes contacts R3 and R4 and opens contacts R5 and Rs. Opening of contact N3 does not deenergize solenoid U, inasmuch as contact U1 is closed and consequently conductor It?! is connected to the line 86 through contacts U9 and R3, while conductor Hid is grounded through contacts U10 and R4. Contacts U3 to Us being closed, current is supplied to the slip rings so as to position the armatures of the several motors in exactly the same positions with respect to their fields after they have been stopped by the dynamic braking. The closing of contact N4 b the deenergization of solenoid N supplies current to heating coil W which, after a time delay sufficient to Permit the above-described positioning of the armatures, opens contact W1 to thereby de-energize solenoid U. Consequently, all or the U contacts are opened and the supply of current to the fields, slip rings and heating coil W is interrupted.

If the pilot wishes to decrease the speeds of the motors, he turns the arm 64 in a counterclockwise direction into contact with segment 53 to thus energize solenoids Z and M. Inasmuch as the contacts M2 and N2 are connected in para allel and contacts M3 and N3 are also connected in parallel, current will be supplied to the field windings and to the slip rings in order to positlon the armature in exactly the same manner as above described when the 64 was turned clockwise to energize relay N However, contacts M5 and Mr,- are closed so as to connect the conductor 1M to the line 80 and conductor I06 to ground, whereas, when relay N was energized, conductor rat was connected to ground and conductor 555 connected to the line. The effect of this is to reverse the polarity of the armatures of the several motors with respect to their fields, and consequentl the motors run in the opposite direction, so as to reduce the tension on the speeder springs and to drive the disc 56 in a counterclockwise direction. When the contact between the arm 64 and the segment 58 is broken, the motors are dynamically braked and angularly positioned with respect to their fields in the same manner as above described.

Should the flight engineer, who normall has control of the switches 56 and 25, wish to change the speed of one of the engines with respect to the speed of the other, he may do so by means of these switches. Closing the contact i l of switch I6 causes the motor having the armature 855 to rotate in the direction which changes the setting of the associated governor so as to increase the tension oi the governor speeder spring, which in turn increases the speed of the associated engine, while closing the contact decreases the speed of the engine. Lik wise, closing contact 24 of switch 25 increases the speed of the other engine, while closing contact decreases the speed of this engine.

When contact M is closed, a circuit is established from the line H3 through the limit witch It, solenoid D, switch it, normally closed contact Y1 and solenoid A to ground. Should, hou ever, the governor 'eady be at the extreme pcsik tion towards whi the closing of contact it would drive it, limit switch 12 will be open and the circuit will not be completed. Assuming ho ever, the switch I2 is closed, energization of solenoid A opens contact A1 and closes contact A2, thus energizing solenoid C through normally closed contact Energication of solenoid C closes c ntact (33, thus connecting conductor 99 to the line 80 to thereb supply excitation current to the field windings of the various motors. Energization oi solenoid D closes contacts D2 and D2 and opens contact D1. Closing of D2 connects the lower brush of armature 86 to conductor H0 and hence to line M, inasmuch as contact Z11 is closed, while closing of D3 connects the upper brush of this commutator through normally closed Contact Z10 to the ground wire I08. Consequently, the armature 86 is rotated, but the other armatures do not rotate because none of the solenoids F, H, or J is energized, Due to the fact that the solenoid U has not been energized, the contacts Us to Ua are all open and hence the slip rings of the various motors are not connected in parallel. Therefore, the motor having the armature 86 may operate independently of the others. This motor continues to operate until either the flight engineer opens the contact H! or the rack H4 driven by this motor reaches its extreme position to thereby open the limit switch I 2, in either of which events the solenoids A and D are lie-energized. Solenoid C, however, remains energized due to the fact that contact C1 is closed and therefore field current is supplied through the contact C3. De-energization of solenoid D opens contacts D2 and D3 to interrupt the supply of current to armature 8G, and closes contact Dr to provide a short circuit of the armature which, inasmuch as the field remains cxcited, dynamically brakes this motor, De-energization of solenoid A closes contact A1, and inasmuch as contact C2 is closed, current is supplied to the heating coil B. After a delay sufficient for the dynamic braking to take place, the coil 13 is heated sufficiently to open contact B1, thus de energizing solenoid C. This, in turn, opens contact C2 to drop out heating coil B, and opens contact C3 to interrupt the supply of field current. When coil B cools and contact B1 closes, solenoid C is not again energized because both contacts A2 and C1 are now open.

If the rack H4 has been driven to its extreme position, limit switch i2 is closed to thus complete a circuit through solenoid K and the signal lamps 46 and E8. One of these lamps is located in the flight engineer's compartment, while the other is located in the pilots compartment, and the lighting thereof notifies both of these officers that the governor is at one or the other of its extreme positions.

Energization of solenoid K by the closing of limit switch l2 opens contact K1 to thus make impossible the energization of solenoid N if the pilot should turn the arm 64 into contact with segment 85. If the governor driven by the armature SE is already at its extreme position for maximum engine speed, it obviously cannot be driven any further in this direction and if the pilot attempts to drive it further, he is prevented from doing so due to the fact that contact K1 is open. However, the pilot may cause all of the motors to run in the opposite direction by turning arm 54 into contact with segment 58 to thus energize solenoids Z and M. In the manner previously described, this first positions all of the armatures with respect to their fields and then causes the motors to run in synchronism in the proper direction to decrease the governor settings. The settings or the several governors are hence changed by like amounts and therefore the speeds of the diiferent engines are varied by equal amounts. However, due to the fact that switch l6 was closed so as to change the speed of one engine with respect to that of the other, the two engines are not in synchronism at the time arm 64 is moved into contact with segment 56, and completion of this circuit does not re-synchronize the engines, but as above stated, changes their speeds by equal amounts. Thus, to take a concrete example, assuming that the engines, as controlled by the governors, have a range from 900 to 2700 R. P. M., it will be further assumed that they were running in synchronism at 2590 R. P. M., before switch l6 was closed. If this switch is closed to complete the circuit through contact l4 and left closed, one or the governors will be run to its maximum limit and will open limit switch 12, and close switch 12 with the result that the speed of the engine controlled thereby will be increased to its maximum of 2700 R. P. M., while the other engine continues to run at 2500 R. P. M. Under these conditions, if the pilot turns arm 64 into contact with segment 60, nothing happens because contact K1 has been opened through the energization of relay K resulting from the closing of limit switch l2. However, if the pilot turns the arm 64 into contact with segment 58 through the proper angle to reduce the speed of the one engine, for example from 2500 to 2200 R. P. the speed of the other engine will be reduced an equal amount, namely from 2700 to 2400 R. P. M.

If, instead of increasing the speed of one engine, the flight engineer wishes to decrease its speed, he throws switch 16 from its neutral or off position so as to complete the circuit through contact 20. Consequently, solenoids A, C and E are energized in the same manner as solenoids A, C and D were energized when the switch [6 was closed in the opposite position. Contact C3 is thus closed to excite the fields 54, 95 and 98 and contact E1 is opened and contacts E2 and E: are closed. Consequently, the lower brush of armature 86 is connected through Z11 and E3 to the ground wire Hi8 and the upper brush is connected through Z10 and E2 and wire Hit to the line 8B. Thus, the polarity of armature 85 has been reversed with respect to what it was when solenoid D was energized to close contacts D2 and D3, and hence the armature rotates in the opposite direction so as to decrease the governor setting, which in turn reduces the speed of the engine controlled thereby.

In a similar manner, the fiight engineer may vary the speed of the other engine by manipulating the switch 2%. Closing this switch through contact 24 energizes solenoids A, C and F to close contact C3 to excite the field windings and to close contacts F2 and F3 to thereby connect the lower brush of armature 84 through contacts Z7, F2 and wire I Hi to line 89 and to connect the upper brush through contacts Z6 and F3 to the ground wire I58. Contact F1 is opened to open the dynamic braking short circuit and consequently armature 84 rotates in the proper direction to increase the setting of the governor associated therewith and hence to increase the speed of the in the opposite direction so as to decrease the governor setting. through contact 24, the governor willbe driven to its extreme maximum range, whereupon limit switch 22 is opened and switch 22 is closed.

Opening of switch 22 tie-energizes solenoid F in the same manner that opening of limit switch [2 de-energized solenoid D, while closing of limit switch 22' energizes solenoid K and lights the signal lamps 5E and 52. If the switch 25 is left closed through contact 353, limit switch 23 will be opened and switch 23 closed when the governor is driven to its minimum limit. Opening of switch 28 deenergizes solenoid G so as to stop the armature 84, while the closing of limit switch 28' lights the signal lamps 5E! and 52 and energizes the solenoid L. As above described, energizing of solenoids K or L opens the contacts K1 or L1, respectively, so as to prevent the energization of solenoids N or M, respectively, in the event that the pilot should turn the contact arm 64 in a direction which would If the switch 26 is left closed tend to run the motor having the armature 84 past its limit position.

If the pilot wishes to re-synchronize the engines he may do so at any time by turning the arm (54 all the way to the right so as to close the switch 65, or all the way to the left so as to close the switch Turning the arm to the right will synchronize the engines at their minimum speed, while turning it to the left will synchronize them at their maximum speed. Thereafter, the pilot may change the synchronous speeds of the engines to any value desired by turning the arm 64 through the proper angle in the manner first described above.

Assuming that the pilot wishes to re-synchronize the engines at the maximum speed, turning of the arm 6 to the left in order to close switch first completes the circuit through the arm and the segment iii} so as to energize solenoids Z and N. Ehis closes contacts N2 and N3. ihe closing of the latter contact energizes solenoid U through normally closed contacts W1 and Y7 and supplies current to the heating coil T through the normally closed contact R2. Energization of solenoid U closes all the U contacts and consequently excites the fields and supplies current to the slip rings 33, Q0 and 92 of the various motors so as to tend to position their armatures with respect to their fields. However, before heating coil T has time to heat suificiently to close contact T1 so as to energize solenoid R, which would result in the motors running in synchronism, the arm 6d closes switch 68 so as to energize solenoid Y. This opens contacts Y1, Y3, Y5 and Y7 and closes contacts Y4 and Y6. Opening of contact Y5 de-energizes solenoid N to thus close contact N1 and to open contacts N2 and N3. Closing of contact N1 energizes solenoid P inasmuch as this solenoid is connected through contact Ye, segment 6E1, arm 54 and signal lamp M to ground. Although contact Y4 is closed, solenoid Q is not energized because arm 84 is not in contact with segment 58 and hence no circuit is completed through the solenoid. Opening of contact Y1 immediately de-energizes solenoid U, thus opening all of the U contacts and disconnecting the slip rings from the wire liill and H32 and hence from each other.

In the event either or both of the switches l5 and 26 are closed at the instant that the pilot closes the switch 63 to re-synchronize the engines, the opening of contact Y1 interrupts the circuit or circuits thus completed through any of the solenoids D, E, F or G. At the same time, the closing of contact Y2 connects the solenoid A to the line iii through the resistor ll. Inasmuch as this resistor has the same resistance as the solenoids D, E, F or G, the same voltage is applied to the solenoid A as is applied when solenoid A is connected to the line iii in series with any of the solenoids D, E, F or G. Energization of the solenoid A closes contact A2 to thus energize solenoid C which results in the closing of contact C3 so as to supply excitation current to the field. windings.

Energization of solenoid P closes contacts P1, P2 and P; so as to energize solenoids D, F and H, respectively, and closes-contact P5 to provide a holding circuit for solenoid P through resistor til to ground. Normally closed contact P4 is opened so as to ale-energize solenoid Z, thus opening contacts Z1, Z4, Z5, Zs, Z9, and Z12 and closing contacts Z2, Z3, Z6, Z7, Z10 and Z11. Energization of solenoids D, and. H opens contacts D1, F1

' and H1, so as to open the dynamic short circuit of each armature, and closes contacts D2, D3, F2, F3, H2, and H3 so as to connect the lower brush of each armature to conductor H and hence to the line 80, and to connect the upper brush of each armature to the ground wire I08. Consequently, the armatures 84 and 85 will rotate in the proper direction to increase the tension on the speeder springs of the respective governors, and the armature B2 will drive the disc 56 in a clockwise direction so to bring the insulated space between the segments 58 and 60 into alignment with the arm 64. The motors will not operate in synchronism, due to the fact that the contacts Us to Us are opened, but each motor will run until it actuates its limit switches. Thus, armature 86 will rotate until limit switch 12 is opened to thereby drop out solenoid D, which opens contacts D2 and D3 to interrupt the supply of current to the commutator and closes contact D1 to dynamically brake this motor. This, however, doe not interfere with the operation of the other motors and consequently armature 84 will rotate until it opens limit switch 22 to drop out solenoid F, while armature 82 will run until it rotates disc 55 sufiiciently to bring the insulated space between segments 58 and 63 into alignment with arm 64. This drops out solenoid H which interrupts the supply of current to, and dynamically brakes armature 82.

Should armature 82 rotate disc 56 to the off position before either or both of the other motors have reached their limits, opening of the circuit through arm 64 and segment 60 will not drop out solenoid P because of the holding circuit established through contact P5 and resistor 69 to ground.

Consequently, the settings of both of the governors have now been re-synchronized at their maximum settings and therefore both of the engines have been synchronized at maximum speed, while the disc 56 has been rotated so as to break the contact between segment 60 and arm 64. Thereafter, the pilot may synchronously decrease the settings of the governors if he wishes the engines to run at something less than their maximum speed, by turning the arm 64 counterclockwise into contact with segment 58. This opens the switch 68, thus de-energizing solenoid Y and opening contact Y2, so as to de-energize solenoid A. This in turn closes contact A1, thus supplying current to the heating coil B, with the result that contact B1 is opened to drop out solenoid C, as has been previously described. Contact Ye is also opened to drop out solenoid P.

Should the pilot wish to maintain the engines at their maximum speed, he will not turn the arm 64 counter-clockwise and hence switch 58 remains closed and solenoids Y, P, A and C remain energized. This is not objectionable except that it consumes a small amount of current and the energization of solenoid C keeps contact Ca closed and the fields excited. However, it will rarely, if ever, occur in practice that the pilot will keep the engines at their maximum speed for any substantial length of time.

The provision of contact Y2 in series with the switches l6 and 26 is necessary in order to eliminate the possibility of a short circuit in the event the pilot re-synchronizes the engines at the same time that one or both of these switches are closed. If, for instance, contact 20 of switch I6 is closed, solenoid E is energized and contacts E2 and E: closed. Under these conditions, if arm 64 is turned so as to close limit switch 68, it energizes solenoid Y which closes contact Yes to energize solenoid P which closes contacts Pi and P: to energize solenoids D and F. Energization of solenoid D closes contacts D2 and D3, and if contacts E2 and E3 were still closed, line 83 would be connected directly to the ground wire I08. However, as soon as solenoid Y is energized it opens contact Y1 to immediately drop out solenoid E, thus opening contacts E2 and E3 to prevent such a short circuit.

If, instead of having turned the arm $4 all the way to the left so as to re-synchronize the engines at their maximum speed, the pilot turns it all the way to the right, so as to re-synchronize them at their minimum speed, this closes the limit switch 66 which energizes the solenoid Y in the same manner as previously described, in asmuch as the switches 66 and 58 are connected in parallel. However, under these conditions the solenoid P is not energized because arm 54 is not in contact with segment 68. On the other hand, solenoid Q is energized through contact Y4, segment 58, arm 64 and signal lamp 7:5. This closes contacts Q1, Q2, Q3, and Q5 to energize solenoids E, G and J and to provide a holding circuit for solenoid Q, and opens contact Q4 so as to drop out solenoid Z. Energization of solonoids E, G and J opens contacts E1, G1 and J1 to remove the dynamic brake short circuit and closes contacts E2, E3, G2, G3, J2 and J3 so as to connect the lower brush of each commutator to the ground wire I08 and to connect the upper brush to the line. Thus, the polarity of the armatures is reversed and the motors operate in the proper direction to decrease the settings of the governors and to rotate the disc 55 in a counterclockwise direction. The armatures and 84 rotate until they open limit switche l8 and 28 and armature 82 rotates until it has driven disc 56 to the Oh position to thus de-energize the relays E, G and J. In this manner, the engines are re-synchronized at their minimum speed and thereafter the pilot may change the governor settings by turning the arm 54 to the left into contact with segment 60 so as to cause the engines to run in synchronism at any desired speed.

It will thus be seen that I have provided a control system for the engines of a multiengine aircraft by means of which the substantially synchronous speed of the engines are at all times under control of the pilot, who may adjust the speeds to any value within their operational limits by merely a single manual manipulation of a switch. In addition, however, the system permits the speeds of the several engines to be adjusted individually by the manipulation of a separate switch for each engine, which switches may be under the control of an officer other than the pilot, such as the flight engineer, inasmuch as the pilot may at any time substantially resynchronize the engines independently of any control which has been or is being exercised by the flight engineer.

By the expression settings of the motors as used in the claims is meant the number of revolutions the motors are away from their limits. Thus, the settings of the motors are the same, or in other words the settings are in synchronism, if all of the motors must rotate the same number of revolutions in order to actuate their respective limit switches, whereas if the several motors must rotate different numbers of revolutions before they actuate their limit switches, their settings are different. It will be noted too, that the motors may rotate in synchronism even though their settings are not in synchronism. Thus, if the flight engineer has momentarily closed one of the switches H or 26 so as to operate motors 86 ort-l, respectively, independently of the other motors to thereby change its setting with respect to the settings of the remaining motors, and thereafter the pilot turns the arm 64 into contact with either segment 53 or 60, but not far enough to actuate either switch 66 or 68, all of the motors will run in synchronism and their respective settings will be changed by equal amounts, but the settings will not be re-synchronized unless the arm 6 is turned far enough to close either switch 65 or 68, whereupon the several motors will be run independently to one or the other of their limits. This changes their respective settings by unequal amount to thereby brin the settings back into synchronism.-

While I have shown and described a system suitable for controlling the governors of two aircraft engines, obviously, any number of governors or other devices may be controlled by adding an electric motor for each additional device and by adding a switch similar to switches It and 26 for each additional motor, each additional switch controlling a pair of solenoids connected thereto in the same manner 'as the pairs D and E, or F and G. Further modifications apparent to a person skilled in the art may be made without departing from the scope of my invention, which is to be limited only by the appended claims.

What I claim is:

1. In a control system, a plurality of similar electric motors, each motor having a field and a wound rotor including a commutator, taps connected to similar fixed points on the rotors of said motors, manually controlled relay means for supplying current to said fields, for connecting said taps in parallel and for supplying current to said tap-s to position said rotors, a time delay relay actuated by the first mentioned relay for subsequently interrupting the supply of current to said taps and for supplying current to said commutators to cause said rotors to run in synchronism, and separately manually controlled relay means for supplying current to said fields and said commutators while said taps are disconnected to cause said motors to run individually.

2. In an electric system, a plurality of electric motors, means for starting, running a selected amount between limits and stopping said motors in synchronism to thereby change the settings of the motors by equal amounts, means for operating each motor independently of the other motors a sel cted amount within said limits to change its setting with respect to that of the other motors, and means for operating all of said motors independently until each motor reaches the same one of said limits to thereby re-synchronize the settings of said motors.

3. In an electric system, a plurality of electric motors, switching mechanism including a manually movable member for starting, running and stopping said motors in synchronism to change the settings of the several motors equal amounts, separate switch s for operating each motor independently to change its setting with respect to that of the other motors, and switching means operable by said member for re-synchronizing the settings of said motors.

4. In an electric system, a plurality of electric motors, switching mechanism including a man ually movable member for starting, running a selected amount between limits and stopping said motors in synchronism to thereby change the settings of the motors by equal amounts, separate switches for operating each motor independently of the other motors a selected amount within said limits to change its setting with respect to that of the other motors, and switching means operable by said member for operating all of said motors independently until each motor reaches the same one of said limits to thereby re-synchronize the settings of said motors.

5. In an electric system, a plurality of electric motors, switching mechanism including a member movable in one direction to cause said motors to start, run in one direction and stop in synchronism and movable in the other direction to cause said motors to start, run in the opposite direction and stop in synch'ronism to thereby change the settings of the several motors by equal amounts, a separate double throw switch for each motor, means responsive to closure of each switch in one position to run the respective motor independently in one direction and responsive to closure of each switch in the other position to run the respective motor independently in the other direction to change its setting with respect to that of the other motors, and switching means operable by said member for rendering said separate switches inoperative to run said motors and for re-synchronizing the settings of said motors.

6. In an electric system, a plurality of electric motors, switching mechanism including a member movable in one direction to cause said motors to start, run in one direction a selected amount within limits and stop in synchronism and movable in the other direction to cause said motors to start, run in the opposite direction a selected amount within said limits and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, means responsive to closure of each switch in one position to run the respective motor independently in one direction a selected amount within said limits and responsive to closure of each switch in the other position to run the respective motor independently in the opposite direction a selected amount Within said limits to change its setting with respect to that of the other motors, and switchin means operable by said member for rendering said separate switches inoperative to run said motors and operable for running all or said motors independently in the same direction until each motor reaches the same one of said limits to thereby re-synchro-nize the settings of said motors.

'7. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movement of said member in one direction to cause said motors to start, run in one direction and stop in synchronisrn and ac tuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure f each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect to that of the other motors, and manually controllable relay means for ire-synchronizing the settings of said motors.

8. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movement of said member in one direction to cause said motors to start, run in one direction and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect to that of the other motors, and relay means actuated by an extreme movement of said member for rc-synchronizing the settings of said motors.

9. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movement of said member in one direction to cause said motors to start, run in one direction and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respec tive motor independently in the opposite direction to change its setting with respect to that of the other motors, and relay means actuated by an extreme movement of said member for runing said motors independently to resynchronize the settings of said motors.

10. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movement of member in one direction to cause s id motors to start, run in one direction and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch {or each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect to that of the other motors, and manually controllable relay means for rendering the second-mentioned relay means inoperative and for re-synchronizing the settings of said motors.

11. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movement of said member in one direction to cause said motors to start, run in one direction and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the oppo site direction and stop in synchrcnism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect to that of the other motors, and manually controllable rclay means for rendering the second-mentioned relay means inoperative and for running said motors independently to ro-synchronize the of said motors.

12. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movemen of said member in one direction to cause said motors to start, run in one direction and stop in syncl'ironism and actu ated by movement of said member in the other direction to cause said motors to start, run in the opposite direction and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each swi ch in one position to run the respective motor independently in one direction and actuated by closure oi each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect to that of the other motors, and relay means actuated by an extreme movement of said member for rendering the second-mentioned relay means inopcrative and for running said motors independently to re-synchr. nice the settings of said meters.

13. In an electric system, a plurality of electric motors, switching mechanisi 1 including a member manually movable in either direction, relay means actuated by movement of said member in one direction to cause said motors to start, run in on direction a selected amount between limits and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction a selected amount between said limits and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect to that of the other motors, and manually controllable relay means {or running all of said motors independently until each motor reaches the same one of said limits to thereby re-syncl'irm nize the settings of said motors.

14. In an electric system, a plura ity of electric motors, switching mechanism including member manually movable in either direction, relay means actuated b movement of said member ill one direction to cause said. motors to start, run in one direction a selected amount between limits and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction a selected amount bet iveen said limits and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respective motor independendently in the opposite direction to change its setting with respect to that of the other motors, and relay means actuated by an extreme movement of said member for running all of said motors independently until each motor reaches the same one of said limits to thereby re-synchronize the settings of said motors.

15. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movement of said member in one direction to cause said motors to start, run in one direction a selected amount between limits and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction a selected amount between said limits and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect to that of the other motors, and manually controllable relay means for rendering the second-mentioned relay means inoperative and for running all of said motors independently until each motor reaches the same one of said limits to thereby re-synchronize the settings of said motors.

16. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movement of said member in one direction to cause said motors to start, run in one direction a selected amount between limits and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction a selected amount between said limits and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect to that of the other motors, a pair of limit switches associated with each motor, one switch of each pair being arranged to be actuated when the motor associated therewith has been operated to one of said limits and the other switch of said pair being arranged to be actuated when the motor associated therewith has been operated to the other of said limits, said switches being so connected that actuation thereof stops the associated motor, and manually controllable relay means for running all of said motors independently until each motor actuates one of said limit switches, whereby the settings of said motors are ire-synchronized at said one of said limits.

17. In an electric system, a plurality of electric motors, switching mechanism including a member manually movable in either direction, relay means actuated by movement of said member in one direction to cause said motors to start, run in one direction a selected amount between limits and stop in synchronism and actuated by movement of said member in the other direction to cause said motors to start, run in the opposite direction a selected amount between said limits and stop in synchronism to thereby change the settings of the several motors by equal amounts in either direction, a separate double throw switch for each motor, relay means actuated by closure of each switch in one position to run the respective motor independently in one direction and actuated by closure of each switch in the opposite position to run the respective motor independently in the opposite direction to change its setting with respect -to that of the other motors, a pair of limit switches associated with each motor, one switch of each pair being arranged to be actuated when the motor associated therewith has been operated to one of said limits and the other switch of said pair being arranged to be actuated when the motor associated therewith has been operated to the other of said limits, said switches being so connected that actuation thereof renders the first-mentioned relay means inoperative to run said motors in synchronism, and manually controllable means for running all of said motors independently until the respective motors are at one of said limits to thereby re-synchronize the settings of said motors.

ERIC C. WAHLBERG. 

